Muscle Wire testing.
TEST 1: Establish basic performance
The purpose of this test is to test the lifting and time related performance of a single Muscle Wire fibre. The outputs from this experiment will consist of a set of performance curves which show contraction and relaxation times of muscle wires under varying loads and varying input power as well as contraction distance. Power input will be varied altering circuit current at a number of fixed voltage levels.
The experimental process will be as follows:
1). The 500 millimetre length of 375 micrometer diameter Muscle Wire fibre is crimped at both ends to a length of anchoring wire. The strength of the crimps is critical as they must be capable of transferring the load attached to the end.
The crimping method was to place the both the Muscle Wire fibre and the anchoring wire into an N-scale model railroad joiner crimp. For added strength two applications of Super Glue were applied and allowed to cure overnight to ensure maximum strength.
Figure 1- Muscle Wire crimping
2). The crimped Muscle Wire will be attached to the test rig as shown below. The electrical circuit will be formed by attaching one lead from the DC power source to the Muscle Wire on the inside of the crimp, a second lead from the Muscle Wire to a multimeter and thirdly connecting the multimeter to the power source as shown in figure 2 below.
Figure 2 - experimental setup for test 1
3). The circuit will be activated for short periods of time at a number of voltage and current levels starting at 800 milliamps and 10 Volts to 3000 milliamps and 14 Volts (with increments of 200 milliamps for each voltage step of 2 Volts). For each power setting the following will be recorded:
Þ Input power (measured in Watts): will include current and voltage levels.
Þ Mass lifted (measured in kilograms)
Þ Total contraction distance (measured in millimetres)
Þ Contraction time (measured in seconds): the time for the wire to go from fully relaxed length to fully contracted length
Þ Retraction time (measured in seconds): the time for the wire to go from fully contracted length back to fully relaxed length.
4).
The experiment
will be repeated for varying mass, 
, and a set of performance curves plotted. Showing the effect
of mass and power on contraction/relaxation times.
TEST 2: Effects of bundling
The purpose of this test is to test determine the effects (if any) on bundling multiple muscle wires on the total lifting capacity and timed contraction relaxation response. Two configurations of multiple Muscle Wires will be tested. Firstly the wires will be tested in a circular array (as shown in the left of figure 3 below) whereby there is four wires arranged even around a disk to give enough air between each wire to simulate individual activation. Secondly, the four wires will be intertwined to create a bundle (figure 3 right). In this configuration, it is expected that heat interaction effects will reduce time related performance (at least in the relaxation phase). It is the aim of this experiment to provide some output on the ability to stack Muscle Wire to increase lifting capacity and to investigate advantages and limitations of such a configuration.
The experimental process will be as follows:
1). The 500 millimetre length of 375 micrometer diameter Muscle Wire fibre is crimped in the same method as discussed in test 1.
2). The circuit setup is as shown in the left of figure __ below with the wires evenly spaced around the disk configuration.
Figure 3- experimental setup for test 2
3).
The circuit with
the spaced Muscle Wire configuration will be activated for short periods of time
at a number of voltage and current levels as in the previous test. In this case
large masses will be used and large currents. A safe operating value for
current and voltage levels will be investigated prior to the test. It is
expected that the system will be able to lift large masses in the order of
to 
times that for a single wire (where
is the number of wires).
The following parameters will be measured:
Þ Input power (measured in Watts): will include current and voltage levels.
Þ Mass lifted (measured in kilograms)
Þ Total contraction distance (measured in millimetres)
Þ Contraction time (measured in seconds): the time for the wire to go from fully relaxed length to fully contracted length
Þ Retraction time (measured in seconds): the time for the wire to go from fully contracted length back to fully relaxed length.
4). A bundle of Muscle Wires will be tested. The bundle will be formed from wires of the same length attached to a coincident point at the at the top and bottom anchor points. The second configuration will then be tested in the same way with the same output measurements.
5). Timed performance, power requirement and overall lifting capacity will then be compared for both configurations
TEST 3: Effects of a simple cooling system
As has been previously discussed one of the main issues with successful application of Muscle Wires to an actuation system is the ability to gain fast response in terms of contraction and relaxation and to be able to control the contraction. The purpose of this test is to explore the effect of three different cooling methods on the time related performance and controllability of single and bundled Muscle Wire configurations.
In this experiment two methods of cooling will be investigated and are briefly described below:
· Fan cooled. A medium size fan or several small fans will be used to direct cool air onto the Muscle Wire fibre during first the relaxation phase, and secondly both the contraction and relaxation phases.
· Silicon heatsink compound and fan cooled. Silicon heat sink compound has very good heat transfer properties and it is hoped that this will be able to transfer some of the heat away from the wires yo enable shorter relaxation times. To test this, the wire(s) is coated in a silicon heatsink compound and a fan(s) is used to cool the wire. Again this will be tested first during the relaxation phase and secondly during both the contraction and relaxation phases.
This test will be broken into two parts:
· Firstly, this experiment will test the timed performance of Muscle Wires in terms of contraction and relaxation rates using the two different cooling methods described above. Two wire configurations will be tested which include a single Muscle Wire fibre (as used in the first test) and a bundle of four wires (as in the second part of test two).
· The second part of this experiment will test the controllability of Muscle Wires in terms of ability to balance a load at partial contraction both with and without application of a cooling system.
Figure 4 - experimental setup for test 3
The experimental process will be as follows:
PART 1: Performance Testing
1). The 500 millimetre length of 375 micrometer diameter Muscle Wire fibre is crimped in the same method as discussed in test 1.
2). A main fan or number of smaller fans will be directed at the Muscle Wire fibre. The wire will be actuated at the current and voltage levels described in the first test. The fan will be activated during the relaxing phase. The retraction time will be recorded.
3). The above step is repeated with the fan activated and directed at the Muscle Wire for both contraction and relaxation phases. Both contraction and retraction time will be recorded.
4). Apply a coating of a silicon heatsink compound to the Muscle Wire and repeat steps 2 and 4.
PART 2: Control
1). Using the same crimped Muscle Wire as before, activate the circuit and when partial contraction has occurred, lower the current to try and keep the weight at a fixed height which is less than the maximum contraction distance. Measure the height the weight reaches and the total time that the weight is held stationary.
2). Repeat the above step using the fan(s) directed.
3). Apply a coating of a silicon heatsink compound to the Muscle Wire and repeat step 2.
Both parts of the experiment will be repeated for the bundle configuration described above in test two.
TEST 4: Activation around a drum
